How vaping affects the ocular surface
Electronic cigarettes (e-cigarettes) are devices designed to deliver nicotine in a solution rather than smoke without tobacco combustion. Perceived by consumers as a safer alternative to conventional cigarettes, e-cigarettes are aggressively marketed as lifestyle-choice consumables.
My father began smoking unfiltered tobacco cigarettes when he was 16 years old. When he was 49, he died of lung cancer. My brother started smoking in college-he has quit smoking, only to begin again more times than I care to remember.
Each battle was accompanied by the side effects of nicotine withdrawal that include anxiety, depression, insomnia, and weight gain. Smoking is a topic that is top of mind for me and for my patients.
Previously from Dr. Mastrota: 5 things you need to know about TFOS DEWS II
Growing vaping community
Electronic cigarettes (e-cigarettes) are devices designed to deliver nicotine in a solution rather than smoke without tobacco combustion. Perceived by consumers as a safer alternative to conventional cigarettes, e-cigarettes are aggressively marketed as lifestyle-choice consumables.
An e-cigarette or electronic nicotine delivery system (ENDS) is a battery-powered vaporizer that simulates tobacco smoking.
E-cigarettes or vape pens (vape means to inhale the vapor produced by an electronic cigarette or similar device) and vape mods are similar devices but are so called because of the specific vaporizing materials they use: e-cigarettes are marketed specifically for “e-juices” or “e-liquids.”
The e-liquids are manufactured in a selection of tempting flavors-candy, cereal, custards, fruity, beverage, tobacco, among many others-as well as titrated nicotine-containing strengths.
Vaping has its own glossary of terms. Vaping can be practiced with more experienced users at vape lounges, cafes, or “cloud chasing” events.1 Notably, in August 2016, the U.S. Food and Drug Administration (FDA) extended its regulatory authority to all tobacco products, including e-cigarettes, that did not previously fall under the FDA’s authority.
Related: The role of lid hygiene in ocular surface disease
Of note, one study culled comments from e-cigarette users from a content analysis of public postings on Twitter on the users’ rationale for vaping. The data suggested that the reasons people vape are shifting away from cessation of combustible use (regular cigarettes) and toward social image.2
Vaping as an aid to discontinuing conventional cigarettes has mixed results. A recent Swiss study found no beneficial effects of vaping at follow-up visits for either smoking cessation or smoking reduction.3
Despite the burgeoning worldwide consumption of e-cigarettes, their safety remains largely unproven, and it is unknown whether these devices cause in vivo toxicological effects that could contribute to cancer. In a rat lung model, co-mutagenic and cancer-initiating effects of e-cigarette vapor was demonstrated.4
Another question: How does vaping impact the ocular surface?
Smoking and health
Tobacco smoking, as we all are aware, is detrimental to overall health and is associated with ocular surface disease. A 2016 meta-analysis suggests that smoking may associate with the risk of dry eye in general population.5
Furthermore, a separate study concluded that smoking might decrease tear secretion, goblet cell density, and tear MUC5AC concentration.6 These studies corroborate a 2008 study by Matsumoto.7
Also, consider secondhand smoke. Secondhand smoke (also called environmental tobacco smoke, involuntary smoke, and passive smoke) is the smoke given off by a burning tobacco product and the smoke exhaled by a smoker.
The National Cancer’s Institute’s Fact Sheet on Secondhand Smoke notes that there is no safe level of exposure, with even low levels of secondhand smoke being harmful.8
Related: Ocular surface disease limits surgical options
The Johnson & Johnson Ocular Surface and Visual Optics Department at Keio University of Medicine in Japan investigated the effects of acute passive cigarette smoke exposure on the ocular surface and the tear film in healthy non-smokers.
Researchers found that even after brief exposure, adverse effects on ocular surface health was evidenced by an increase of tear inflammatory cytokines, tear instability, and damage to the ocular surface epithelia.9
Similarly, Ward et al showed that passive exposure to cigarette smoke is associated with an increase in tear instability and damage to the ocular surface epithelia in soft contact lens wearers and non-contact lens wearers.10
Of added concern, passive smoking represents a significant risk factor of dry eye in children.11
To parallel, let us consider secondhand vape. Logue et al computed the integrated health damage from passive vaping. This was derived by computing disability-adjusted life years (DALYs) lost due to exposure of toxic compounds in secondhand vapor.
Acrolein and other compounds including formaldehyde were the contributors to aggregate harm.12,13
DALYs for the various vape device and voltage combinations were lower than or comparable to those estimated for exposures to secondhand and thirdhand tobacco smoke. Thirdhand smoke is residual nicotine and other chemicals left on indoor surfaces by tobacco smoke.
This residue is thought to react with common indoor pollutants to create a toxic mix, including cancer-causing compounds, posing a potential health hazard to nonsmokers, especially children.12,13
Aldehydes are emitted by electronic cigarettes due to thermal decomposition of liquid components. Overheating produces an unpleasant taste-called a dry puff-and elevated levels of aldehydes, which vapers learn to avoid.14
The vaping market
Why have electronic cigarettes become popular? They do not contain tobacco, although they do use nicotine from tobacco plants. They do not generate cigarette smoke but rather an aerosol.
An aerosol is a suspension of fine particles of liquid, solid, or both in a gas: both the particulate and gas phases are mixtures of chemical substances in e-cigarette aerosols15) that is frequently but inaccurately referred to as vapor (a vapor is a substance in the gas phase).
Related: It’s all about the ocular surface!
E-cigarettes sales reached $2.76B U.S. in 2014 and are expected to grow to $10B U.S. this year.16 They are readily available for purchase in convenience stores, smoke shops, mall kiosks, supermarkets, or even online, while traditional cigarettes shipments are regulated.
Adult e-cigarette use is increasing globally, and early studies have suggested that similar trends may be observed among the adolescent population. A 2014 literature review suggests that adolescents are nearing complete awareness of e-cigarettes;17 however, relatively low observed number of patients with ENDS use documented in electronic health records (EHR) suggests vast under documentation.18
Alarmingly, one in four U.S. high school teens who has used e-cigarettes has also tried a potentially dangerous new vaping method called “dripping”-dropping e-cigarette liquid directly onto the hot coils of the device to produce thicker, more flavorful vapor.19
Similarly, adolescent users of e-cigarettes and other electronic vaping products (EVPs) report performing “vape tricks” (exhaling aerosol to make shapes).
Vape tricks pose a potential threat to adolescent health because they may encourage nonusers to initiate or current EVP users to use more frequently or switch to advanced devices that produce more harmful chemical emissions.20 “Vape-bending (tricks)” tutorials are readily available on an Internet search.
Of note, however, the number of high school and middle school students using electronic cigarettes fell to 2.2 million in 2016 from 3 million in 2015, according to 2017 survey by the Centers for Disease Control and Prevention (CDC).21
E-cigarettes and health
Environmental concerns as well as concerns regarding non-user exposure also exist. The health impact of e-cigarettes for users and the public cannot be determined with currently available data.22 While e-cigarette aerosol may contain fewer toxicants than cigarette smoke, studies evaluating whether e-cigarettes are less harmful than cigarettes are inconclusive.
Related: A new tool for managing ocular surface disease
In response to the growing public health concern regarding the risks or benefits of e-cigarette use relative to smoking, the National Institute on Drug Abuse (NIDA) has recently introduced the first standardized and well-characterized e-cig device to the research community.23
The availability of the NIDA Standard Research e-cigarette offers a exceptional research opportunity with tremendous public health implications.
Comparing and contrasting the cancer-causing potentials of standard vaping and smoking in youth will help determine the health risks or benefits of e-cigarette use relative to cigarette smoking.
This information will be instrumental in making scientifically based decisions on the development and evaluation of policies and regulations on e-cigarette manufacture, marketing, and distribution.
Ultimately, evidence-based guidelines and legislations on e-cigarettes may help reduce the burden of tobacco-related diseases, particularly on minors and vulnerable populations. I suspect that this work will guide investigation to vaping effects-or not-on the ocular surface.24
A PubMed “e-cigarette dry eye/ocular surface” search in early September 2017 yielded no results. You can find a case, however, that describes extensive ocular injury secondary to an e-cigarette-related explosion. The explosion was the result of modifications made to a heating element of the e-cigarette device.25
I eagerly await studies on this topic and until then suspect that the use of ENDS negatively impact the ocular surface environment. I am certain we will revisit this critical topic in the months to come.
References
1. Blu. Vaping Glossary. Available at: https://www.blu.com/en/US/explore/explore-vaping/vaping-glossary.html. Accessed 9/4/17.
2. Ayers JW, Leas EC, Allem JP, Benton A, Dredze M, Althouse BM, Cruz TB, Unger JB. Why do people use electronic nicotine delivery systems (electronic cigarettes)? A content analysis of Twitter, 2012-2015. PLoS One. 2017 Mar 1;12(3):e0170702.
3. Gmel G, Baggio S, Mohler-Kuo M, Daeppen JB, Studer J. E-cigarette use in young Swiss men: is vaping an effective way of reducing or quitting smoking? Swiss Med Wkly. 2016 Jan 11;146:w14271.
4. Canistro D, Vivarelli F, Cirillo S, Babot Marquillas C, Buschini A, Lazzaretti M, Marchi L, Cardenia V, Rodriguez-Estrada MT, Lodovici M, Cipriani C, Lorenzini A, Croco E, Marchionni S, Franchi P, Lucarini M, Longo V, Della Croce CM, Vornoli A, Colacci A, Vaccari M, Sapone A, Paolini M. E-cigarettes induce toxicological effects that can raise the cancer risk. Sci Rep. 2017 May 17;7(1):2028.
5. Xu L, Zhang W, Zhu XY, Suo T, Fan XQ, Fu Y. Smoking and the risk of dry eye: a Meta-analysis. Int J Ophthalmol. 2016 Oct 18;9(10):1480-1486.
6. Uchino Y, Uchino M, Yokoi N, Dogru M, Kawashima M, Komuro A, Sonomura Y, Kato H, Argüeso P, Kinoshita S, Tsubota K. Impact of Cigarette Smoking on Tear Function and Correlation between Conjunctival Goblet Cells and Tear MUC5AC Concentration in Office Workers. Sci Rep. 2016 Jun 14;6:27699.
7. Matsumoto Y, Dogru M, Goto E, Sasaki Y, Inoue H, Saito I, Shimazaki J, Tsubota K. Alterations of the tear film and ocular surface health in chronic smokers. Eye (Lond). 2008 Jul;22(7):961-8.
8. National Cancer Institute. Secondhand Smoke and Cancer. at: http://www.cancer.gov/cancertopics/factsheet/Tobacco/ETS. Accessed 9/24/17. Available
9. Rummenie VT, Matsumoto Y, Dogru M, Wang Y, Hu Y, Ward SK, Igarashi A, Wakamatsu T, Ibrahim O, Goto E, Luyten G, Inoue H, Saito I, Shimazaki J, Tsubota K.Tear cytokine and ocular surface alterations following brief passive cigarette smoke exposure. Cytokine. 2008 Aug;43(2):200-8.
10. Ward SK, Dogru M, Wakamatsu T, Ibrahim O, Matsumoto Y, Kojima T, Sato EA, Ogawa J, Schnider C, Negishi K, Tsubota K. Passive cigarette smoke exposure and soft contact lens wear. Optom Vis Sci. 2010 May;87(5):367-72.
11. El-Shazly AA, El-Zawahry WM, Hamdy AM, Ahmed MB. Passive smoking as a risk factor of dry eye in children. J Ophthalmol. 2012;2012:130159.
12. Hays JT. What is thirdhand smoke, and why is it a concern? Mayo Clinic. Available at: http://www.mayoclinic.org/healthy-lifestyle/adult-health/expert-answers/third-hand-smoke/faq-2005779. Accessed 9/5/2017
13. Logue JM, Sleiman M, Montesinos VN, Russell ML, Litter MI, Benowitz NL, Gundel LA, Destaillats H. Emissions from Electronic Cigarettes: Assessing Vapers' Intake of Toxic Compounds, Secondhand Exposures, and the Associated Health Impacts. Environ Sci Technol. 2017 Aug 15;51(16):9271-9279.
14. Farsalinos KE, Voudris V, Poulas K. E-cigarettes generate high levels of aldehydes only in 'dry puff' conditions. Addiction. 2015 Aug;110(8):1352-6.
15. Cheng T. Chemical evaluation of electronic cigarettes. Tob Control. 2014 May;23 Suppl 2:ii11-7.
16. Electronic cigarettes (e-cigarettes) dollar sales worldwide from 2008 to 2017 (in million U.S. dollars). Statista. Available at: https://www.statista.com/statistics/493214/global-e-cigarettes-dollar-sales/. Accessed 9/4/2017.
17. Greenhill R, Dawkins L, Notley C, Finn MD, Turner JJ. Adolescent Awareness and Use of Electronic Cigarettes: A Review of Emerging Trends and Findings. J Adolesc Health. 2016 Dec;59(6):612-619.
18. Young-Wolff KC, Klebaner D, Folck B, Carter-Harris L, Salloum RG, Prochaska JJ, Fogelberg R, Tan ASL. Do you vape? Leveraging electronic health records to assess clinician documentation of electronic nicotine delivery system use among adolescents and adults. Prev Med. 2017 Aug 16;105:32-36.
19. Krishnan-Sarin S, Morean M, Kong G, Bold KW, Camenga DR, Cavallo DA, Simon P, Wu R. E-Cigarettes and "Dripping" Among High-School Youth. Pediatrics. 2017 Mar;139(3). pii: e20163224.
20. Pepper JK, Lee YO, Watson KA, Kim AE, Nonnemaker JM, Farrelly MC. Risk Factors for Youth E-Cigarette "Vape Trick" Behavior. Adolesc Health. 2017 Jun 29. pii: S1054-139X(17)30215-X.
21. New Surveys Suggest Teen Vaping Rates Falling. NY Times. Available at: https://www.nytimes.com/2017/06/19/health/teen-vaping.html. Accessed 9/4/2017.
22. Callahan-Lyon P. Electronic cigarettes: human health effects. Tob Control. 2014 May;23 Suppl 2:ii36-40.
23. National Institute on Drug Abuse. Supplemental Information for NIDA e-cig. Available at: https://www.drugabuse.gov/funding/supplemental-information-nida-e-cig. Accessed 9/24/17.
24. Besaratinia A, Tommasi S. An opportune and unique research to evaluate the public health impact of electronic cigarettes. Cancer Causes Control. 2017 Aug 31. doi: 10.1007/s10552-017-0952-5.
25. Khairudin MN, Mohd Zahidin AZ, Bastion ML. Front to back ocular injury from a vaping-related explosion. BMJ Case Rep. 2016 Apr 5;2016. pii: bcr2016214964.
